This thesis is on peer group grey games. First of all cooperative game theory; cooperative interval games and cooperative peer group games are investigated. Then, peer group situations and related games are given. Peer group situations are modeled as peer group grey games by using grey numbers, which is the main contribution of the thesis to the literature. Finally, applications of peer group grey situations to several Operations Research situatons are given. Keywords: Peer group situations, peer group games, grey numbers, cooperative game theory, value, Shapley value, Operations Research.Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Matematik Anabilim Dalı, 2017.Kaynakça var.This thesis is on peer group grey games. First of all cooperative game theory; cooperative interval games and cooperative peer group games are investigated. Then, peer group situations and related games are given. Peer group situations are modeled as peer group grey games by using grey numbers, which is the main contribution of the thesis to the literature. Finally, applications of peer group grey situations to several Operations Research situatons are given. Keywords: Peer group situations, peer group games, grey numbers, cooperative game theory, value, Shapley value, Operations Research.